H-Cys(aminoethyl)-OH · HCl is a cysteine-derived amino acid derivative that contains the cysteine backbone bearing an aminoethyl side-chain, classifying it as a modified amino acid with an additional primary amine functionality beyond the native thiol-containing side chain. As the hydrochloride salt, the molecule exists as a protonated salt form, featuring free carboxylic acid and amino groups while the side-chain aminoethyl group is available for nucleophilic reactions and conjugation chemistry. In peptide and bioconjugation workflows, it is used as a chemically defined building block for introducing an extra cationic handle for linker formation, crosslinking, or structure-activity studies involving polyamine-like spacing.
CAT No: CP27097
CAS No:4099-35-8
Synonyms/Alias:L-4-Thialysine · HCl;L-Thiosine · HCl
H-Cys(aminoethyl)-OH · HCl is a cysteine-derived amino acid hydrochloride featuring a free amino acid backbone with a side chain extended by an additional aminoethyl substituent, providing two nitrogen-containing functionalities in the same molecule. The compound bears a chiral center at the cysteine α-position and is supplied as the hydrochloride salt, which increases water compatibility and influences amine protonation during coupling and derivatization. The presence of a thiol group enables selective redox and nucleophilic chemistry, while the extra primary amine supports orthogonal protection strategies and subsequent functional group installation. As an amino acid-based intermediate, it is suitable for peptide building block preparation, side-chain functionalization, and downstream synthesis of polyamine-like motifs that can be incorporated into chemically defined scaffolds.
1. Peptide Synthesis
H-Cys(aminoethyl)-OH · HCl is applied in peptide synthesis workflows where cysteine-like coupling chemistry is required alongside an additional side-chain amine for orthogonal protection and controlled reactivity. The thiol group can be managed through thiol-protecting-group strategies during amide bond formation, while the aminoethyl side chain can be protected to prevent undesired cross-reactions during N- or C-terminal activation. The hydrochloride salt form supports handling in aqueous or mixed solvents during protected amino acid preparation and subsequent coupling steps. The resulting protected derivatives can serve as building blocks for peptides and peptide fragments that contain both sulfur and amine functionalities for controlled post-coupling modification.
2. Chemical Biology Conjugation
H-Cys(aminoethyl)-OH · HCl is suited to chemical biology and biomolecule modification strategies that require thiol-directed conjugation paired with a second amine handle for linker design. The thiol functionality can be converted into reactive intermediates or maintained under selective protection to enable chemoselective attachment to carriers, while the aminoethyl group enables attachment of additional tags, affinity motifs, or solubilizing groups. Salt-state protonation from the hydrochloride form can be leveraged to tune amine reactivity during conjugation planning and purification. Downstream derivatives can be used to generate defined bioconjugates, including amino acid-based linkers and multifunctional conjugation reagents for mechanistic studies and analytical labeling.
3. Unnatural Amino Acid Incorporation
H-Cys(aminoethyl)-OH · HCl functions as a chiral amino acid intermediate for unnatural amino acid incorporation into peptides and peptidomimetic scaffolds. The α-amino acid stereocenter supports stereochemically defined incorporation, while the aminoethyl side chain introduces a polyamine-like motif that can alter charge distribution, binding interactions, and conformational preferences. Protecting-group planning can separate the thiol and side-chain amine reactivity to maintain compatibility with peptide coupling and subsequent functional transformations. The compound can therefore be translated into protected analogs for structure-activity relationship studies and molecular design efforts that probe how side-chain nitrogen density and sulfur chemistry influence recognition.
4. Side-Chain Functionalization
H-Cys(aminoethyl)-OH · HCl is used in side-chain functionalization routes where dual functionality enables sequential derivatization from sulfur and nitrogen sites. The thiol group can participate in nucleophilic substitution, redox-controlled transformations, or conversion to thiol-reactive intermediates, whereas the aminoethyl primary amine can undergo acylation, alkylation, or formation of amide and urea linkages. The hydrochloride salt form helps maintain amine protonation during early-stage intermediate preparation, supporting reproducible handling and controlled protection/deprotection sequences. Resulting functionalized derivatives can be employed as intermediates for crosslinkers, charged building blocks, and chemically defined scaffolds used in synthetic organic chemistry and applied research.
5. Process Chemistry Intermediate
H-Cys(aminoethyl)-OH · HCl is relevant to process chemistry and fine chemical synthesis as a chiral, multifunctional amino acid intermediate that can be manufactured and further converted into protected amino acid derivatives. The combination of thiol and aminoethyl amine enables straightforward downstream branching into multiple product classes, including protected cysteine analogs, amine-functional intermediates, and thiol-reactive derivatives. Salt formation as the hydrochloride can improve storage and handling characteristics by moderating free-base amine variability and supporting consistent feed composition for subsequent protection and coupling chemistry. The compound's structural features make it suitable for scalable synthesis planning where orthogonal protection strategies are used to manage functional group compatibility across manufacturing steps.
6. Analytical Research Standards
H-Cys(aminoethyl)-OH · HCl can be used in analytical research settings to prepare reference materials and derivatization reagents for amino acid profiling and thiol/amine detection workflows. The defined stereochemistry and known functional group pattern support method development for chromatographic separation and mass spectrometric characterization of cysteine-like and polyamine-like species. The thiol and aminoethyl amine can be derivatized to generate stable analytical derivatives, enabling consistent detection and quantitation of related compounds in complex mixtures. The hydrochloride salt form also supports reproducible sample preparation and calibration strategies for studies involving amino acid derivatives and peptide hydrolysates.
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